Internet DRAFT - draft-carpenter-anima-gdn-protocol
draft-carpenter-anima-gdn-protocol
Network Working Group B. Carpenter
Internet-Draft Univ. of Auckland
Intended status: Standards Track B. Liu
Expires: December 22, 2015 Huawei Technologies Co., Ltd
June 20, 2015
A Generic Discovery and Negotiation Protocol for Autonomic Networking
draft-carpenter-anima-gdn-protocol-04
Abstract
This document establishes requirements for a signaling protocol that
enables autonomic devices and autonomic service agents to dynamically
discover peers, to synchronize state with them, and to negotiate
parameter settings mutually with them. The document then defines a
general protocol for discovery, synchronization and negotiation,
while the technical objectives for specific scenarios are to be
described in separate documents. An Appendix briefly discusses
existing protocols with comparable features.
Status of This Memo
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This Internet-Draft will expire on December 22, 2015.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirement Analysis of Discovery, Synchronization and
Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements for Discovery . . . . . . . . . . . . . . . 4
2.2. Requirements for Synchronization and Negotiation
Capability . . . . . . . . . . . . . . . . . . . . . . . 6
2.3. Specific Technical Requirements . . . . . . . . . . . . . 8
3. GDNP Protocol Overview . . . . . . . . . . . . . . . . . . . 9
3.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 9
3.2. High-Level Design Choices . . . . . . . . . . . . . . . . 11
3.3. GDNP Protocol Basic Properties and Mechanisms . . . . . . 14
3.3.1. Required External Security Mechanism . . . . . . . . 15
3.3.2. Transport Layer Usage . . . . . . . . . . . . . . . . 15
3.3.3. Discovery Mechanism and Procedures . . . . . . . . . 15
3.3.4. Negotiation Procedures . . . . . . . . . . . . . . . 17
3.3.5. Synchronization Procedure . . . . . . . . . . . . . . 18
3.4. GDNP Constants . . . . . . . . . . . . . . . . . . . . . 20
3.5. Session Identifier (Session ID) . . . . . . . . . . . . . 20
3.6. GDNP Messages . . . . . . . . . . . . . . . . . . . . . . 20
3.6.1. GDNP Message Format . . . . . . . . . . . . . . . . . 21
3.6.2. Discovery Message . . . . . . . . . . . . . . . . . . 21
3.6.3. Response Message . . . . . . . . . . . . . . . . . . 22
3.6.4. Request Message . . . . . . . . . . . . . . . . . . . 22
3.6.5. Negotiation Message . . . . . . . . . . . . . . . . . 23
3.6.6. Negotiation-ending Message . . . . . . . . . . . . . 23
3.6.7. Confirm-waiting Message . . . . . . . . . . . . . . . 23
3.7. GDNP General Options . . . . . . . . . . . . . . . . . . 24
3.7.1. Format of GDNP Options . . . . . . . . . . . . . . . 24
3.7.2. Divert Option . . . . . . . . . . . . . . . . . . . . 24
3.7.3. Accept Option . . . . . . . . . . . . . . . . . . . . 25
3.7.4. Decline Option . . . . . . . . . . . . . . . . . . . 25
3.7.5. Waiting Time Option . . . . . . . . . . . . . . . . . 26
3.7.6. Device Identity Option . . . . . . . . . . . . . . . 27
3.7.7. Locator Options . . . . . . . . . . . . . . . . . . . 27
3.8. Objective Options . . . . . . . . . . . . . . . . . . . . 29
3.8.1. Format of Objective Options . . . . . . . . . . . . . 29
3.8.2. General Considerations for Objective Options . . . . 30
3.8.3. Organizing of Objective Options . . . . . . . . . . . 30
3.8.4. Vendor Specific Objective Options . . . . . . . . . . 31
3.8.5. Experimental Objective Options . . . . . . . . . . . 32
4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 32
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5. Security Considerations . . . . . . . . . . . . . . . . . . . 36
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 38
8. Change log [RFC Editor: Please remove] . . . . . . . . . . . 39
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.1. Normative References . . . . . . . . . . . . . . . . . . 40
9.2. Informative References . . . . . . . . . . . . . . . . . 41
Appendix A. Capability Analysis of Current Protocols . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46
1. Introduction
The success of the Internet has made IP-based networks bigger and
more complicated. Large-scale ISP and enterprise networks have
become more and more problematic for human based management. Also,
operational costs are growing quickly. Consequently, there are
increased requirements for autonomic behavior in the networks.
General aspects of autonomic networks are discussed in [RFC7575] and
[RFC7576]. A reference model for autonomic networking is given in
[I-D.behringer-anima-reference-model]. In order to fulfil autonomy,
devices that embody autonomic service agents have specific signaling
requirements. In particular they need to discover each other, to
synchronize state with each other, and to negotiate parameters and
resources directly with each other. There is no restriction on the
type of parameters and resources concerned, which include very basic
information needed for addressing and routing, as well as anything
else that might be configured in a conventional non-autonomic
network. The atomic unit of synchronization or negotiation is
referred to as a technical objective, i.e, a configurable parameter
or set of parameters (defined more precisely in Section 3.1).
Following this Introduction, Section 2 describes the requirements for
discovery, synchronization and negotiation. Negotiation is an
iterative process, requiring multiple message exchanges forming a
closed loop between the negotiating devices. State synchronization,
when needed, can be regarded as a special case of negotiation,
without iteration. Section 3.2 describes a behavior model for a
protocol intended to support discovery, synchronization and
negotiation. The design of Generic Discovery and Negotiation
Protocol (GDNP) in Section 3 of this document is mainly based on this
behavior model. The relevant capabilities of various existing
protocols are reviewed in Appendix A.
The proposed discovery mechanism is oriented towards synchronization
and negotiation objectives. It is based on a neighbor discovery
process, but also supports diversion to off-link peers. Although
many negotiations will occur between horizontally distributed peers,
many target scenarios are hierarchical networks, which is the
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predominant structure of current large-scale managed networks.
However, when a device starts up with no pre-configuration, it has no
knowledge of the topology. The protocol itself is capable of being
used in a small and/or flat network structure such as a small office
or home network as well as a professionally managed network.
Therefore, the discovery mechanism needs to be able to allow a device
to bootstrap itself without making any prior assumptions about
network structure.
Because GDNP can be used to perform a decision process among
distributed devices or between networks, it must run in a secure and
strongly authenticated environment.
It is understood that in realistic deployments, not all devices will
support GDNP. It is expected that some autonomic service agents will
directly manage a group of non-autonomic nodes, and that other non-
autonomic nodes will be managed traditionally. Such mixed scenarios
are not discussed in this specification.
2. Requirement Analysis of Discovery, Synchronization and Negotiation
This section discusses the requirements for discovery, negotiation
and synchronization capabilities. The primary user of the protocol
is an autonomic service agent (ASA), so the requirements are mainly
expressed as the features needed by an ASA. A single physical device
might contain several ASAs, and a single ASA might manage several
technical objectives.
2.1. Requirements for Discovery
1. ASAs may be designed to manage anything, as required in
Section 2.2. A basic requirement is therefore that the protocol can
represent and discover any kind of technical objective among
arbitrary subsets of participating nodes.
In an autonomic network we must assume that when a device starts up
it has no information about any peer devices, the network structure,
or what specific role it must play. The ASA(s) inside the device are
in the same situation. In some cases, when a new application session
starts up within a device, the device or ASA may again lack
information about relevant peers. It might be necessary to set up
resources on multiple other devices, coordinated and matched to each
other so that there is no wasted resource. Security settings might
also need updating to allow for the new device or user. The relevant
peers may be different for different technical objectives. Therefore
discovery needs to be repeated as often as necessary to find peers
capable of acting as counterparts for each objective that a discovery
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initiator needs to handle. From this background we derive the next
three requirements:
2. When an ASA first starts up, it has no knowledge of the specific
network to which it is attached. Therefore the discovery process
must be able to support any network scenario, assuming only that the
device concerned is bootstrapped from factory condition.
3. When an ASA starts up, it must require no information about any
peers in order to discover them.
4. If an ASA supports multiple technical objectives, relevant peers
may be different for different discovery objectives, so discovery
needs to be repeated to find counterparts for each objective. Thus,
there must be a mechanism by which an ASA can separately discover
peer ASAs for each of the technical objectives that it needs to
manage, whenever necessary.
5. Following discovery, an ASA will normally perform negotiation or
synchronization for the corresponding objectives. The design should
allow for this by associating discovery, negotiation and
synchronization objectives. It may provide an optional mechanism to
combine discovery and negotiation/synchronization in a single call.
6. Some objectives may only be significant on the local link, but
others may be significant across the routed network and require off-
link operations. Thus, the relevant peers might be immediate
neighbors on the same layer 2 link, or they might be more distant and
only accessible via layer 3. The mechanism must therefore provide
both on-link and off-link discovery of ASAs supporting specific
technical objectives.
7. The discovery process should be flexible enough to allow for
special cases, such as the following:
o In some networks, as mentioned above, there will be some
hierarchical structure, at least for certain synchronization or
negotiation objectives, but this is unknown in advance. The
discovery protocol must therefore operate regardless of
hierarchical structure, which is an attribute of individual
technical objectives and not of the autonomic network as a whole.
This is part of the more general requirement to discover off-link
peers.
o During initialisation, a device must be able to establish mutual
trust with the rest of the network and join an authentication
mechanism. Although this will inevitably start with a discovery
action, it is a special case precisely because trust is not yet
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established. This topic is the subject of
[I-D.pritikin-anima-bootstrapping-keyinfra]. We require that once
trust has been established for a device, all ASAs within the
device inherit the device's credentials and are also trusted.
o Depending on the type of network involved, discovery of other
central functions might be needed, such as a source of Intent
distribution [RFC7575] or the Network Operations Center (NOC)
[I-D.eckert-anima-stable-connectivity]. The protocol must be
capable of supporting such discovery during initialisation, as
well as discovery during ongoing operation.
8. The discovery process must not generate excessive (multicast)
traffic and must take account of sleeping nodes in the case of a
resource-constrained network [RFC7228].
2.2. Requirements for Synchronization and Negotiation Capability
As background, consider the example of routing protocols, the closest
approximation to autonomic networking already in widespread use.
Routing protocols use a largely autonomic model based on distributed
devices that communicate repeatedly with each other. The focus is
reachability, so current routing protocols mainly consider simple
link status, i.e., up or down, and an underlying assumption is that
all nodes need a consistent view of the network topology in order for
the routing algorithm to converge. Thus, routing is mainly based on
information synchronization between peers, rather than on bi-
directional negotiation. Other information, such as latency,
congestion, capacity, and particularly unused capacity, would be
helpful to get better path selection and utilization rate, but is not
normally used in distributed routing algorithms. Additionally,
autonomic networks need to be able to manage many more dimensions,
such as security settings, power saving, load balancing, etc. Status
information and traffic metrics need to be shared between nodes for
dynamic adjustment of resources and for monitoring purposes. While
this might be achieved by existing protocols when they are available,
the new protocol needs to be able to support parameter exchange,
including mutual synchronization, even when no negotiation as such is
required. In general, these parameters do not apply to all
participating nodes, but only to a subset.
9. A basic requirement for the protocol is therefore the ability to
represent, discover, synchronize and negotiate almost any kind of
network parameter among arbitrary subsets of participating nodes.
10. Negotiation is a request/response process that must be
guaranteed to terminate (with success or failure) and if necessary it
must contain tie-breaking rules for each technical objective that
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requires them. While these must be defined specifically for each use
case, the protocol should have some general mechanisms in support of
loop and deadlock prevention, such as hop count limits or timeouts.
11. Synchronization might concern small groups of nodes or very
large groups. Different solutions might be needed at different
scales.
12. To avoid "reinventing the wheel", the protocol should be able to
carry the message formats used by existing configuration protocols
(such as NETCONF/YANG) in cases where that is convenient.
13. Human intervention in complex situations is costly and error-
prone. Therefore, synchronization or negotiation of parameters
without human intervention is desirable whenever the coordination of
multiple devices can improve overall network performance. It
therefore follows that the protocol, as part of the Autonomic
Networking Infrastructure, must be capable of running in any device
that would otherwise need human intervention.
14. Human intervention in large networks is often replaced by use of
a top-down network management system (NMS). It therefore follows
that the protocol, as part of the Autonomic Networking
Infrastructure, must be capable of running in any device that would
otherwise be managed by an NMS, and that it can co-exist with an NMS,
and with protocols such as SNMP and NETCONF.
15. Some features are expected to be implemented by individual ASAs,
but the protocol must be general enough to allow them:
o Dependencies and conflicts: In order to decide a configuration on
a given device, the device may need information from neighbors.
This can be established through the negotiation procedure, or
through synchronization if that is sufficient. However, a given
item in a neighbor may depend on other information from its own
neighbors, which may need another negotiation or synchronization
procedure to obtain or decide. Therefore, there are potential
dependencies and conflicts among negotiation or synchronization
procedures. Resolving dependencies and conflicts is a matter for
the individual ASAs involved. To allow this, there need to be
clear boundaries and convergence mechanisms for negotiations.
Also some mechanisms are needed to avoid loop dependencies. In
such a case, the protocol's role is limited to signaling between
ASAs.
o Recovery from faults and identification of faulty devices should
be as automatic as possible. The protocol's role is limited to
the ability to handle discovery, synchronization and negotiation
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at any time, in case an ASA detects an anomaly such as a
negotiation counterpart failing.
o Since the goal is to minimize human intervention, it is necessary
that the network can in effect "think ahead" before changing its
parameters. In other words there must be a possibility of
forecasting the effect of a change by a "dry run" mechanism before
actually installing the change. This will be an application of
the protocol rather than a feature of the protocol itself.
o Management logging, monitoring, alerts and tools for intervention
are required. However, these can only be features of individual
ASAs. Another document [I-D.eckert-anima-stable-connectivity]
discusses how such agents may be linked into conventional OAM
systems via an Autonomic Control Plane
[I-D.behringer-anima-autonomic-control-plane].
16. The protocol will be able to deal with a wide variety of
technical objectives, covering any type of network parameter.
Therefore the protocol will need either an explicit information model
describing its messages, or at least a flexible and extensible
message format. One design consideration is whether to adopt an
existing information model or to design a new one.
2.3. Specific Technical Requirements
17. It should be convenient for ASA designers to define new
technical objectives and for programmers to express them, without
excessive impact on run-time efficiency and footprint. The classes
of device in which the protocol might run is discussed in
[I-D.behringer-anima-reference-model].
18. The protocol should be extensible in case the initially defined
discovery, synchronization and negotiation mechanisms prove to be
insufficient.
19. To be a generic platform, the protocol payload format should be
independent of the transport protocol or IP version. In particular,
it should be able to run over IPv6 or IPv4. However, some functions,
such as multicasting or broadcasting on a link, might need to be IP
version dependent. In case of doubt, IPv6 should be preferred.
20. The protocol must be able to access off-link counterparts via
routable addresses, i.e., must not be restricted to link-local
operation.
21. It must also be possible for an external discovery mechanism to
be used, if appropriate for a given technical objective. In other
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words, GDNP discovery must not be a prerequisite for GDNP negotiation
or synchronization; the prerequisite is discovering a peer's locator
by any method.
22. ASAs and the signaling protocol engine need to run
asynchronously when wait states occur.
23. Intent: There must be provision for general Intent rules to be
applied by all devices in the network (e.g., security rules, prefix
length, resource sharing rules). However, Intent distribution might
not use the signaling protocol itself, but its design should not
exclude such use.
24. Management monitoring, alerts and intervention: Devices should
be able to report to a monitoring system. Some events must be able
to generate operator alerts and some provision for emergency
intervention must be possible (e.g. to freeze synchronization or
negotiation in a mis-behaving device). These features might not use
the signaling protocol itself, but its design should not exclude such
use.
25. The protocol needs to be fully secured against forged messages
and man-in-the middle attacks, and secured as much as reasonably
possible against denial of service attacks. It needs to be capable
of encryption in order to resist unwanted monitoring, although this
capability may not be required in all deployments. However, it is
not required that the protocol itself provides these security
features; it may depend on an existing secure environment.
3. GDNP Protocol Overview
3.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119] when they appear in ALL CAPS. When these words are not in
ALL CAPS (such as "should" or "Should"), they have their usual
English meanings, and are not to be interpreted as [RFC2119] key
words.
This document uses terminology defined in [RFC7575].
The following additional terms are used throughout this document:
o Discovery: a process by which an ASA discovers peers according to
a specific discovery objective. The discovery results may be
different according to the different discovery objectives. The
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discovered peers may later be used as negotiation counterparts or
as sources of synchronization data.
o Negotiation: a process by which two (or more) ASAs interact
iteratively to agree on parameter settings that best satisfy the
objectives of one or more ASAs.
o State Synchronization: a process by which two (or more) ASAs
interact to agree on the current state of parameter values stored
in each ASA. This is a special case of negotiation in which
information is sent but the ASAs do not request their peers to
change parameter settings. All other definitions apply to both
negotiation and synchronization.
o Technical Objective (usually abbreviated as Objective): A
technical objective is a configurable parameter or set of
parameters of some kind, which occurs in three contexts:
Discovery, Negotiation and Synchronization. In the protocol, an
objective is represented by an identifier (actually a GDNP option
number) and if relevant a value. Normally, a given objective will
occur during discovery and negotiation, or during discovery and
synchronization, but not in all three contexts.
* One ASA may support multiple independent objectives.
* The parameter described by a given objective is naturally based
on a specific service or function or action. It may in
principle be anything that can be set to a specific logical,
numerical or string value, or a more complex data structure, by
a network node. That node is generally expected to contain an
ASA which may itself manage other nodes.
* Discovery Objective: if a node needs to synchronize or
negotiate a specific objective but does not know a peer that
supports this objective, it starts a discovery process. The
objective is called a Discovery Objective during this process.
* Synchronization Objective: an objective whose specific
technical content needs to be synchronized among two or more
ASAs.
* Negotiation Objective: an objective whose specific technical
content needs to be decided in coordination with another ASA.
o Discovery Initiator: an ASA that spontaneously starts discovery by
sending a discovery message referring to a specific discovery
objective.
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o Discovery Responder: a peer ASA which responds to the discovery
objective initiated by the discovery initiator.
o Synchronization Initiator: an ASA that spontaneously starts
synchronization by sending a request message referring to a
specific synchronization objective.
o Synchronization Responder: a peer ASA which responds with the
value of a synchronization objective.
o Negotiation Initiator: an ASA that spontaneously starts
negotiation by sending a request message referring to a specific
negotiation objective.
o Negotiation Counterpart: a peer with which the Negotiation
Initiator negotiates a specific negotiation objective.
3.2. High-Level Design Choices
This section describes a behavior model and some considerations for
designing a generic discovery, synchronization and negotiation
protocol, which can act as a platform for different technical
objectives.
NOTE: This protocol is described here in a stand-alone fashion as a
proof of concept. An early version was prototyped by Huawei and the
Beijing University of Posts and Telecommunications. However, this is
not yet a definitive proposal for IETF adoption. In particular,
adaptation and extension of one of the protocols discussed in
Appendix A might be an option. This whole specification is subject
to change as a result.
o A generic platform
The protocol is designed as a generic platform, which is
independent from the synchronization or negotiation contents. It
takes care of the general intercommunication between counterparts.
The technical contents will vary according to the various
technical objectives and the different pairs of counterparts.
o The protocol is expected to form part of an Autonomic Networking
Infrastructure [I-D.behringer-anima-reference-model]. It will
provide services to ASAs via a suitable application programming
interface, which will reflect the protocol elements but will not
necessarily be in one-to-one correspondence to them. It is
expected that the protocol engine and each ASA will run as
independent asynchronous processes.
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o Security infrastructure and trust relationship
Because this negotiation protocol may directly cause changes to
device configurations and bring significant impacts to a running
network, this protocol is assumed to run within an existing secure
environment with strong authentication.
On the other hand, a limited negotiation model might be deployed
based on a limited trust relationship. For example, between two
administrative domains, ASAs might also exchange limited
information and negotiate some particular configurations based on
a limited conventional or contractual trust relationship.
o Discovery, synchronization and negotiation designed together
The discovery method and the synchronization and negotiation
methods are designed in the same way and can be combined when this
is useful. These processes can also be performed independently
when appropriate.
* GDNP discovery is appropriate for efficient discovery of GDNP
peers and allows a rapid mode of operation described in
Section 3.3.3. For some parameters, especially those concerned
with application layer services, a text-based discovery
mechanism such as DNS Service Discovery
[I-D.ietf-dnssd-requirements] or Service Location Protocol
[RFC2608] might be more appropriate. The choice is left to the
designers of individual ASAs.
o A uniform pattern for technical contents
The synchronization and negotiation contents are defined according
to a uniform pattern. They could be carried either in simple TLV
(Type, Length and Value) format or in payloads described by a
flexible language. The initial protocol design uses the TLV
approach. The format is extensible for unknown future
requirements.
o A flexible model for synchronization
GDNP supports bilateral synchronization, which could be used to
perform synchronization among a small number of nodes. It also
supports an unsolicited flooding mode when large groups of nodes,
possibly including all autonomic nodes, need data for the same
technical objective.
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* There may be some network parameters for which a more
traditional flooding mechanism such as ADNCP
[I-D.ietf-homenet-dncp] [I-D.stenberg-anima-adncp] is
considered more appropriate. GDNP can coexist with ADNCP.
o A simple initiator/responder model for negotiation
Multi-party negotiations are too complicated to be modeled and
there might be too many dependencies among the parties to converge
efficiently. A simple initiator/responder model is more feasible
and can complete multi-party negotiations by indirect steps.
o Organizing of synchronization or negotiation content
Naturally, the technical content will be organized according to
the relevant function or service. The content from different
functions or services is kept independent from each other. They
are not combined into a single option or single session because
these contents may be negotiated or synchronized with different
counterparts or may be different in response time.
o Self-aware network device
Every autonomic device will be pre-loaded with various functions
and ASAs and will be aware of its own capabilities, typically
decided by the hardware, firmware or pre-installed software. Its
exact role may depend on Intent and on the surrounding network
behaviors, which may include forwarding behaviors, aggregation
properties, topology location, bandwidth, tunnel or translation
properties, etc. The surrounding topology will depend on the
network planning. Following an initial discovery phase, the
device properties and those of its neighbors are the foundation of
the synchronization or negotiation behavior of a specific device.
A device has no pre-configuration for the particular network in
which it is installed.
o Requests and responses in negotiation procedures
The initiator can negotiate with its relevant negotiation
counterpart ASAs, which may be different according to the specific
negotiation objective. It can request relevant information from
the negotiation counterpart so that it can decide its local
configuration to give the most coordinated performance. It can
request the negotiation counterpart to make a matching
configuration in order to set up a successful communication with
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it. It can request certain simulation or forecast results by
sending some dry run conditions.
Beyond the traditional yes/no answer, the responder can reply with
a suggested alternative if its answer is 'no'. This would start a
bi-directional negotiation ending in a compromise between the two
ASAs.
o Convergence of negotiation procedures
To enable convergence, when a responder makes a suggestion of a
changed condition in a negative reply, it should be as close as
possible to the original request or previous suggestion. The
suggested value of the third or later negotiation steps should be
chosen between the suggested values from the last two negotiation
steps. In any case there must be a mechanism to guarantee
convergence (or failure) in a small number of steps, such as a
timeout or maximum number of iterations.
* End of negotiation
A limited number of rounds, for example three, or a timeout, is
needed on each ASA for each negotiation objective. It may be
an implementation choice, a pre-configurable parameter, or
network Intent. These choices might vary between different
types of ASA. Therefore, the definition of each negotiation
objective MUST clearly specify this, so that the negotiation
can always be terminated properly.
* Failed negotiation
There must be a well-defined procedure for concluding that a
negotiation cannot succeed, and if so deciding what happens
next (deadlock resolution, tie-breaking, or revert to best-
effort service). Again, this MUST be specified for individual
negotiation objectives, as an implementation choice, a pre-
configurable parameter, or network Intent.
3.3. GDNP Protocol Basic Properties and Mechanisms
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3.3.1. Required External Security Mechanism
The protocol SHOULD run within a secure Autonomic Control Plane (ACP)
[I-D.behringer-anima-autonomic-control-plane]. The procedure for
establishing the ACP MUST provide a flag indicating to GDNP that the
ACP has been established.
If there is no ACP, the protocol MUST use TLS [RFC5246] or DTLS
[RFC6347] for all messages, based on a local Public Key
Infrastructure (PKI) [RFC5280] managed within the autonomic network
itself.
Link-local multicast is used for discovery messages. These cannot be
secured, but responses to discovery messages MUST be secured.
However, during initialisation, before a node has joined the
applicable trust infrastructure, e.g.,
[I-D.pritikin-anima-bootstrapping-keyinfra], it might be impossible
to secure certain messages. Such messages MUST be limited to the
strictly necessary minimum.
3.3.2. Transport Layer Usage
The protocol is capable of running over UDP or TCP, except for link-
local multicast discovery messages, which can only run over UDP and
MUST NOT be fragmented, and therefore cannot exceed the link MTU
size.
When running within a secure ACP, UDP SHOULD be used for messages not
exceeding the minimum IPv6 path MTU, and TCP MUST be used for longer
messages. In other words, IPv6 fragmentation is avoided. If a node
receives a UDP message but the reply is too long, it MUST open a TCP
connection to the peer for the reply.
When running without an ACP, TLS MUST be supported and used by
default, except for multicast discovery messages. DTLS MAY be
supported as an alternative but the details are out of scope for this
document.
For all transport protocols, the GDNP protocol listens to the GDNP
Listen Port (Section 3.4).
3.3.3. Discovery Mechanism and Procedures
o Separated discovery and negotiation mechanisms
Although discovery and negotiation or synchronization are
defined together in the GDNP, they are separated mechanisms.
The discovery process could run independently from the
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negotiation or synchronization process. Upon receiving a
discovery (Section 3.6.2) or request (Section 3.6.4) message,
the recipient ASA should return a message in which it either
indicates itself as a discovery responder or diverts the
initiator towards another more suitable ASA.
The discovery action will normally be followed by a negotiation
or synchronization action. The discovery results could be
utilized by the negotiation protocol to decide which ASA the
initiator will negotiate with.
o Discovery Procedures
Discovery starts as an on-link operation. The Divert option
can tell the discovery initiator to contact an off-link ASA for
that discovery objective. Every DISCOVERY message is sent by a
discovery initiator via UDP to the ALL_GDNP_NEIGHBOR multicast
address (Section 3.4). Every network device that supports the
GDNP always listens to a well-known UDP port to capture the
discovery messages.
If an ASA in the neighbor device supports the requested
discovery objective, it MAY respond with a Response message
(Section 3.6.3) with locator option(s). Otherwise, if the
neighbor has cached information about an ASA that supports the
requested discovery objective (usually because it discovered
the same objective before), it SHOULD respond with a Response
message with a Divert option pointing to the appropriate
Discovery Responder.
If no discovery response is received within a reasonable
timeout (default GDNP_DEF_TIMEOUT milliseconds, Section 3.4),
the DISCOVERY message MAY be repeated, with a newly generated
Session ID (Section 3.5). An exponential backoff SHOULD be
used for subsequent repetitions, in order to mitigate possible
denial of service attacks.
After a GDNP device successfully discovers a Discovery
Responder supporting a specific objective, it MUST cache this
information. This cache record MAY be used for future
negotiation or synchronization, and SHOULD be passed on when
appropriate as a Divert option to another Discovery Initiator.
The cache lifetime is an implementation choice that MAY be
modified by network Intent.
If multiple Discovery Responders are found for the same
objective, they SHOULD all be cached, unless this creates a
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resource shortage. The method of choosing between multiple
responders is an implementation choice.
A GDNP device with multiple link-layer interfaces (typically a
router) MUST support discovery on all interfaces. If it
receives a DISCOVERY message on a given interface for a
specific objective that it does not support and for which it
has not previously discovered a Discovery Responder, it MUST
relay the query by re-issuing the same DISCOVERY message on its
other interfaces. However, it MUST limit the total rate at
which it relays discovery messages to a reasonable value, in
order to mitigate possible denial of service attacks. It MUST
cache the Session ID value of each relayed discovery message
and, to prevent loops, MUST NOT relay a DISCOVERY message which
carries such a cached Session ID. These precautions avoid
discovery loops.
This relayed discovery mechanism, with caching of the results,
should be sufficient to support most network bootstrapping
scenarios.
o A complete discovery process will start with multicast on the
local link; a neighbor might divert it to an off-link destination,
which could be a default higher-level gateway in a hierarchical
network. Then discovery would continue with a unicast to that
gateway; if that gateway is still not the right counterpart, it
should divert to another gateway, which is in principle closer to
the right counterpart. Finally the right counterpart responds to
start the negotiation or synchronization process.
o Rapid Mode (Discovery/Negotiation binding)
A Discovery message MAY include one or more Negotiation
Objective option(s). This allows a rapid mode of negotiation
described in Section 3.3.4. A similar mechanism is defined for
synchronization in Section 3.3.5.
3.3.4. Negotiation Procedures
A negotiation initiator sends a negotiation request to a counterpart
ASA, including a specific negotiation objective. It may request the
negotiation counterpart to make a specific configuration.
Alternatively, it may request a certain simulation or forecast result
by sending a dry run configuration. The details, including the
distinction between dry run and an actual configuration change, will
be defined separately for each type of negotiation objective.
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If the counterpart can immediately apply the requested configuration,
it will give an immediate positive (accept) answer. This will end
the negotiation phase immediately. Otherwise, it will negotiate. It
will reply with a proposed alternative configuration that it can
apply (typically, a configuration that uses fewer resources than
requested by the negotiation initiator). This will start a bi-
directional negotiation to reach a compromise between the two ASAs.
The negotiation procedure is ended when one of the negotiation peers
sends a Negotiation Ending message, which contains an accept or
decline option and does not need a response from the negotiation
peer. Negotiation may also end in failure (equivalent to a decline)
if a timeout is exceeded or a loop count is exceeded.
A negotiation procedure concerns one objective and one counterpart.
Both the initiator and the counterpart may take part in simultaneous
negotiations with various other ASAs, or in simultaneous negotiations
about different objectives. Thus, GDNP is expected to be used in a
multi-threaded mode. Certain negotiation objectives may have
restrictions on multi-threading, for example to avoid over-allocating
resources.
Rapid Mode (Discovery/Negotiation linkage)
A Discovery message MAY include a Negotiation Objective option.
In this case the Discovery message also acts as a Request message
to indicate to the Discovery Responder that it could directly
reply to the Discovery Initiator with a Negotiation message for
rapid processing, if it could act as the corresponding negotiation
counterpart. However, the indication is only advisory not
prescriptive.
This rapid mode could reduce the interactions between nodes so
that a higher efficiency could be achieved. This rapid
negotiation function SHOULD be configured off by default and MAY
be configured on or off by Intent.
3.3.5. Synchronization Procedure
A synchronization initiator sends a synchronization request to a
counterpart, including a specific synchronization objective. The
counterpart responds with a Response message containing the current
value of the requested synchronization objective. No further
messages are needed. If no Response message is received, the
synchronization request MAY be repeated after a suitable timeout.
In the case just described, the message exchange is unicast and
concerns only one synchronization objective. For large groups of
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nodes requiring the same data, synchronization flooding is available.
For this, a synchronization responder MAY send an unsolicited
Response message containing one or more Synchronization Objective
option(s), if and only if the specification of those objectives
permits it. This is sent as a multicast message to the
ALL_GDNP_NEIGHBOR multicast address (Section 3.4). In this case a
suitable mechanism is needed to avoid excessive multicast traffic.
This mechanism MUST be defined as part of the specification of the
synchronization objective(s) concerned. It might be a simple rate
limit or a more complex mechanism such as the Trickle algorithm
[RFC6206].
A GDNP device with multiple link-layer interfaces (typically a
router) MUST support synchronization flooding on all interfaces. If
it receives a multicast unsolicited Response message on a given
interface, it MUST relay it by re-issuing the same Response message
on its other interfaces. However, it MUST limit the total rate at
which it relays Response messages to a reasonable value, in order to
mitigate possible denial of service attacks. It MUST cache the
Session ID value of each relayed discovery message and, to prevent
loops, MUST NOT relay a Response message which carries such a cached
Session ID. These precautions avoid synchronization loops.
Note that this mechanism is unreliable in the case of sleeping nodes.
Sleeping nodes that require an objective subject to synchronization
flooding SHOULD periodically initiate normal synchronization for that
objective.
Rapid Mode (Discovery/Synchronization linkage)
A Discovery message MAY include one or more Synchronization
Objective option(s). In this case the Discovery message also acts
as a Request message to indicate to the Discovery Responder that
it could directly reply to the Discovery Initiator with a Response
message with synchronization data for rapid processing, if the
discovery target supports the corresponding synchronization
objective(s). However, the indication is only advisory not
prescriptive.
This rapid mode could reduce the interactions between nodes so
that a higher efficiency could be achieved. This rapid
synchronization function SHOULD be configured off by default and
MAY be configured on or off by Intent.
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3.4. GDNP Constants
o ALL_GDNP_NEIGHBOR
A link-local scope multicast address used by a GDNP-enabled device
to discover GDNP-enabled neighbor (i.e., on-link) devices . All
devices that support GDNP are members of this multicast group.
* IPv6 multicast address: TBD1
* IPv4 multicast address: TBD2
o GDNP Listen Port (TBD3)
A UDP and TCP port that every GDNP-enabled network device always
listens to.
o GDNP_DEF_TIMEOUT (60000 milliseconds)
The default timeout used to determine that a discovery or
negotiation has failed to complete.
o GDNP_DEF_LOOPCT (6)
The default loop count used to determine that a negotiation has
failed to complete.
3.5. Session Identifier (Session ID)
A 24-bit opaque value used to distinguish multiple sessions between
the same two devices. A new Session ID MUST be generated for every
new Discovery or Request message, and for every unsolicited Response
message. All follow-up messages in the same discovery,
synchronization or negotiation procedure, which is initiated by the
request message, MUST carry the same Session ID.
The Session ID SHOULD have a very low collision rate locally. It is
RECOMMENDED to be generated by a pseudo-random algorithm using a seed
which is unlikely to be used by any other device in the same network
[RFC4086].
3.6. GDNP Messages
This document defines the following GDNP message format and types.
Message types not listed here are reserved for future use. The
numeric encoding for each message type is shown in parentheses.
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3.6.1. GDNP Message Format
GDNP messages share an identical fixed format header and a variable
format area for options. GDNP message headers and options are in the
type-length-value (TLV) format defined in DNCP (see Section "Type-
Length-Value Objects" in [I-D.ietf-homenet-dncp]).
Every GDNP message carries a Session ID. Options are presented
serially in the options field, with padding to 4-byte alignment.
The following diagram illustrates the format of GDNP messages:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MESSAGE_TYPE | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MESSAGE_TYPE: Identifies the GDNP message type. 16-bit.
Reserved: Set to zero, ignored on receipt. 8-bit.
Session ID: Identifies this GDNP session, as defined in Section 3.5.
24-bit.
Options: GDNP Options carried in this message. Options are defined
starting at Section 3.7.
3.6.2. Discovery Message
DISCOVERY (MESSAGE_TYPE = G1):
A discovery initiator sends a DISCOVERY message to initiate a
discovery process.
The discovery initiator sends the DISCOVERY messages to the link-
local ALL_GDNP_NEIGHBOR multicast address for discovery, and stores
the discovery results (including responding discovery objectives and
corresponding unicast addresses or FQDNs).
A DISCOVERY message MUST include exactly one of the following:
o a discovery objective option (Section 3.8.1).
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o a negotiation objective option (Section 3.8.1) to indicate to the
discovery target that it MAY directly reply to the discovery
initiatior with a NEGOTIATION message for rapid processing, if it
could act as the corresponding negotiation counterpart. The
sender of such a DISCOVERY message MUST initialize a negotiation
timer and loop count in the same way as a REQUEST message
(Section 3.6.4).
o one or more synchronization objective options (Section 3.8.1) to
indicate to the discovery target that it MAY directly reply to the
discovery initiator with a RESPONSE message for rapid processing,
if it could act as the corresponding synchronization counterpart.
3.6.3. Response Message
RESPONSE (MESSAGE_TYPE = G2):
A node which receives a DISCOVERY message sends a Response message to
respond to a discovery. It MUST contain the same Session ID as the
DISCOVERY message. It MAY include a copy of the discovery objective
from the DISCOVERY message.
If the responding node supports the discovery objective of the
discovery, it MUST include at least one kind of locator option
(Section 3.7.7) to indicate its own location. A combination of
multiple kinds of locator options (e.g. IP address option + FQDN
option) is also valid.
If the responding node itself does not support the discovery
objective, but it knows the locator of the discovery objective, then
it SHOULD respond to the discovery message with a divert option
(Section 3.7.2) embedding a locator option or a combination of
multiple kinds of locator options which indicate the locator(s) of
the discovery objective.
A node which receives a synchronization request sends a Response
message with the synchronization data, in the form of GDNP Option(s)
for the specific synchronization objective(s).
3.6.4. Request Message
REQUEST (MESSAGE_TYPE = G3):
A negotiation or synchronization requesting node sends the REQUEST
message to the unicast address (directly stored or resolved from the
FQDN) of the negotiation or synchronization counterpart (selected
from the discovery results).
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A request message MUST include the relevant objective option, with
the requested value in the case of negotiation.
When an initiator sends a REQUEST message, it MUST initialize a
negotiation timer for the new negotiation thread with the value
GDNP_DEF_TIMEOUT milliseconds. Unless this timeout is modified by a
CONFIRM-WAITING message (Section 3.6.7), the initiator will consider
that the negotiation has failed when the timer expires.
When an initiator sends a REQUEST message, it MUST initialize the
loop count of the objective option with a value defined in the
specification of the option or, if no such value is specified, with
GDNP_DEF_LOOPCT.
3.6.5. Negotiation Message
NEGOTIATION (MESSAGE_TYPE = G4):
A negotiation counterpart sends a NEGOTIATION message in response to
a REQUEST message, a NEGOTIATION message, or a DISCOVERY message in
Rapid Mode. A negotiation process MAY include multiple steps.
The NEGOTIATION message MUST include the relevant Negotiation
Objective option, with its value updated according to progress in the
negotiation. The sender MUST decrement the loop count by 1. If the
loop count becomes zero both parties will consider that the
negotiation has failed.
3.6.6. Negotiation-ending Message
NEGOTIATION-ENDING (MESSAGE_TYPE = G5):
A negotiation counterpart sends an NEGOTIATION-ENDING message to
close the negotiation. It MUST contain one, but only one of accept/
decline option, defined in Section 3.7.3 and Section 3.7.4. It could
be sent either by the requesting node or the responding node.
3.6.7. Confirm-waiting Message
CONFIRM-WAITING (MESSAGE_TYPE = G6):
A responding node sends a CONFIRM-WAITING message to indicate the
requesting node to wait for a further negotiation response. It might
be that the local process needs more time or that the negotiation
depends on another triggered negotiation. This message MUST NOT
include any other options than the Waiting Time Option
(Section 3.7.5).
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3.7. GDNP General Options
This section defines the GDNP general options for the negotiation and
synchronization protocol signaling. Additional option types are
reserved for GDNP general options defined in the future.
3.7.1. Format of GDNP Options
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-data |
| (option-len octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: An unsigned integer identifying the specific option
type carried in this option.
Option-len: An unsigned integer giving the length of the option-data
field in this option in octets.
Option-data: The data for the option; the format of this data
depends on the definition of the option.
GDNP options are scoped by using encapsulation. If an option
contains other options, the outer Option-len includes the total size
of the encapsulated options, and the latter apply only to the outer
option.
3.7.2. Divert Option
The divert option is used to redirect a GDNP request to another node,
which may be more appropriate for the intended negotiation or
synchronization. It may redirect to an entity that is known as a
specific negotiation or synchronization counterpart (on-link or off-
link) or a default gateway. The divert option MUST only be
encapsulated in Response messages. If found elsewhere, it SHOULD be
silently ignored.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DIVERT | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Option(s) of Diversion Target(s) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_DIVERT (G32).
Option-len: The total length of diverted destination sub-option(s)
in octets.
Locator Option(s) of Diversion Device(s): Embedded Locator Option(s)
(Section 3.7.7) that point to diverted destination target(s).
3.7.3. Accept Option
The accept option is used to indicate to the negotiation counterpart
that the proposed negotiation content is accepted.
The accept option MUST only be encapsulated in Negotiation-ending
messages. If found elsewhere, it SHOULD be silently ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ACCEPT | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_ACCEPT (G33)
Option-len: 0
3.7.4. Decline Option
The decline option is used to indicate to the negotiation counterpart
the proposed negotiation content is declined and end the negotiation
process.
The decline option MUST only be encapsulated in Negotiation-ending
messages. If found elsewhere, it SHOULD be silently ignored.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DECLINE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_DECLINE (G34)
Option-len: 0
Notes: there are scenarios where a negotiation counterpart wants to
decline the proposed negotiation content and continue the negotiation
process. For these scenarios, the negotiation counterpart SHOULD use
a Negotiate message, with either an objective option that contains at
least one data field with all bits set to 1 to indicate a meaningless
initial value, or a specific objective option that provides further
conditions for convergence.
3.7.5. Waiting Time Option
The waiting time option is used to indicate that the negotiation
counterpart needs to wait for a further negotiation response, since
the processing might need more time than usual or it might depend on
another triggered negotiation.
The waiting time option MUST only be encapsulated in Confirm-waiting
messages. If found elsewhere, it SHOULD be silently ignored. When
received, its value overwrites the negotiation timer (Section 3.6.4).
The counterpart SHOULD send a Negotiation, Negotiation-Ending or
another Confirm-waiting message before the negotiation timer expires.
If not, the initiator MUST abandon or restart the negotiation
procedure, to avoid an indefinite wait.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_WAITING | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_WAITING (G35)
Option-len: 4, in octets
Time: Time in milliseconds
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3.7.6. Device Identity Option
The Device Identity option carries the identities of the sender and
of the domain(s) that it belongs to. The format of the Device
Identity option is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DEVICE_ID | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Identities (variable length) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_DEVICE_ID (G36)
Option-len: Length of identities in octets
Identities: A variable-length field containing the device identity
and one or more domain identities. The format is not yet defined.
Note: Currently this option is a placeholder. It might be removed
or modified.
3.7.7. Locator Options
These locator options are used to present reachability information
for an ASA, a device or an interface. They are Locator IPv4 Address
Option, Locator IPv6 Address Option and Locator FQDN (Fully Qualified
Domain Name) Option.
Note that it is assumed that all locators are in scope throughout the
GDNP domain. GDNP is not intended to work across disjoint addressing
or naming realms.
3.7.7.1. Locator IPv4 address option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LOCATOR_IPV4ADDR | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4-Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Option-code: OPTION_LOCATOR_IPV4ADDR (G37)
Option-len: 4, in octets
IPv4-Address: The IPv4 address locator of the target
Note: If an operator has internal network address translation for
IPv4, this option MUST NOT be used within the Divert option.
3.7.7.2. Locator IPv6 address option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LOCATOR_IPV6ADDR | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6-Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_LOCATOR_IPV6ADDR (G38)
Option-len: 16, in octets
IPv6-Address: The IPv6 address locator of the target
Note: A link-local IPv6 address MUST NOT be used when this option is
used within the Divert option.
3.7.7.3. Locator FQDN option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_FQDN | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Fully Qualified Domain Name |
| (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_FQDN (G39)
Option-len: Length of Fully Qualified Domain Name in octets
Domain-Name: The Fully Qualified Domain Name of the target
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Note: Any FQDN which might not be valid throughout the network in
question, such as a Multicast DNS name [RFC6762], MUST NOT be used
when this option is used within the Divert option.
3.8. Objective Options
3.8.1. Format of Objective Options
An objective option is used to identify objectives for the purposes
of discovery, negotiation or synchronization. All objectives must
follow a common format as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_XXX | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flags | loop-count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value |
. (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_XXX: The option code assigned in the
specification of the XXX objective.
option-len: The total length in octets.
flags: Flag bits.
Bit 0 (D bit): set if this objective is valid for GDNP discovery
operations.
Bit 1 (N bit): set if this objective is valid for GDNP negotiation
operations.
Bit 2 (S bit): set if this objective is valid for GDNP
synchronization operations.
Bits 3~7: reserved, set to zero and ignored on reception.
loop-count: The loop count for terminating negotation. This field
is present if and only if the objective is a negotiation
objective.
value: This field is to express the actual value of a negotiation or
synchronization objective. Its format is defined in the
specification of the objective and may be a single value or a data
structure of any kind.
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3.8.2. General Considerations for Objective Options
Objective Options MUST be assigned an option type greater than G63 in
the GDNP option table.
An Objective Option that contains no additional fields, i.e., has a
length of 4 octets, is a discovery objective and MUST only be used in
Discovery and Response messages.
The Negotiation Objective Options contain negotiation objectives,
which are various according to different functions/services. They
MUST be carried by Discovery, Request or Negotiation Messages only.
The negotiation initiator MUST set the initial "loop-count" to a
value specified in the specification of the objective or, if no such
value is specified, to GDNP_DEF_LOOPCT.
For most scenarios, there should be initial values in the negotiation
requests. Consequently, the Negotiation Objective options MUST
always be completely presented in a Request message, or in a
Discovery message in rapid mode. If there is no initial value, the
bits in the value field SHOULD all be set to 1 to indicate a
meaningless value, unless this is inappropriate for the specific
negotiation objective.
Synchronization Objective Options are similar, but MUST be carried by
Discovery, Request or Response messages only. They include value
fields only in Response messages.
3.8.3. Organizing of Objective Options
As noted earlier, one negotiation objective is handled by each GDNP
negotiation thread. Therefore, a negotiation objective, which is
based on a specific function or action, SHOULD be organized as a
single GDNP option. It is NOT RECOMMENDED to organize multiple
negotiation objectives into a single option, nor to split a single
function or action into multiple negotiation objectives.
A synchronization objective SHOULD also be organized as a single GDNP
option.
Some objectives will support more than one operational mode. An
example is a negotiation objective with both a "dry run" mode (where
the negotiation is to find out whether the other end can in fact make
the requested change without problems) and a "live" mode. Such modes
will be defined in the specification of such an objective. These
objectives SHOULD include a "flags" octet, with bits indicating the
applicable mode(s).
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An objective may have multiple parameters. Parameters can be
categorized into two classes: the obligatory ones presented as fixed
fields; and the optional ones presented in TLV sub-options or some
other form of data structure. The format might be inherited from an
existing management or configuration protocol, the objective option
acting as a carrier for that format. The data structure might be
defined in a formal language, but that is a matter for the
specifications of individual objectives. There are many candidates,
according to the context, such as ABNF, RBNF, XML Schema, possibly
YANG, etc. The GDNP protocol itself is agnostic on these questions.
It is NOT RECOMMENDED to split parameters in a single objective into
multiple options, unless they have different response periods. An
exception scenario may also be described by split objectives.
3.8.4. Vendor Specific Objective Options
Option codes G128~159 have been reserved for vendor specific options.
Multiple option codes have been assigned because a single vendor
might use multiple options simultaneously. These vendor specific
options are highly likely to have different meanings when used by
different vendors. Therefore, they SHOULD NOT be used without an
explicit human decision and SHOULD NOT be used in unmanaged networks
such as home networks.
There is one general requirement that applies to all vendor specific
options. They MUST start with a field that uniquely identifies the
enterprise that defines the option, in the form of a registered 32
bit Private Enterprise Number (PEN) [I-D.liang-iana-pen]. There is
no default value for this field. Note that it is not used during
discovery. It MUST be verified during negotiation or
synchronization.
In the case of a vendor-specific objective, the loop count and flags,
if present, follow the PEN.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_vendor | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PEN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flags | loop-count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value |
. (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Option-code: OPTION_vendor (G128~159)
Option-len: The total length in octets.
PEN: Private Enterprise Number.
flags: See Section 3.8.1
loop-count: See Section 3.8.1 This field is present if and only if
the objective is a negotiation objective.
value: This field is to express the actual value of a negotiation or
synchronization objective. Its format is defined in the vendor's
specification of the objective.
3.8.5. Experimental Objective Options
Option codes G176~191 have been reserved for experimental options.
Multiple option codes have been assigned because a single experiment
may use multiple options simultaneously. These experimental options
are highly likely to have different meanings when used for different
experiments. Therefore, they SHOULD NOT be used without an explicit
human decision and SHOULD NOT be used in unmanaged networks such as
home networks.
These option codes are also RECOMMENDED for use in documentation
examples.
4. Open Issues
There are various unresolved design questions that are worthy of more
work in the near future, as listed below (statically numbered in
historical order for reference purposes, with the resolved issues
retained for reference):
o 1. UDP vs TCP: For now, this specification suggests UDP and TCP
as message transport mechanisms. This is not clarified yet. UDP
is good for short conversations, is necessary for multicast
discovery, and generally fits the discovery and divert scenarios
well. However, it will cause problems with large messages. TCP
is good for stable and long sessions, with a little bit of time
consumption during the session establishment stage. If messages
exceed a reasonable MTU, a TCP mode will be required in any case.
This question may be affected by the security discussion.
RESOLVED by specifying UDP for short message and TCP for longer
one.
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o 2. DTLS or TLS vs built-in security mechanism. For now, this
specification has chosen a PKI based built-in security mechanism
based on asymmetric cryptography. However, (D)TLS might be chosen
as security solution to avoid duplication of effort. It also
allows essentially similar security for short messages over UDP
and longer ones over TCP. The implementation trade-offs are
different. The current approach requires expensive asymmetric
cryptographic calculations for every message. (D)TLS has startup
overheads but cheaper crypto per message. DTLS is less mature
than TLS.
RESOLVED by specifying external security (ACP or (D)TLS).
o The following open issues apply only if the current security model
is retained:
* 2.1. For replay protection, GDNP currently requires every
participant to have an NTP-synchronized clock. Is this OK for
low-end devices, and how does it work during device
bootstrapping? We could take the Timestamp out of signature
option, to become an independent and OPTIONAL (or RECOMMENDED)
option.
* 2.2. The Signature Option states that this option could be any
place in a message. Wouldn't it be better to specify a
position (such as the end)? That would be much simpler to
implement.
RESOLVED by changing security model.
o 3. DoS Attack Protection needs work.
RESOLVED by adding text.
o 4. Should we consider preferring a text-based approach to
discovery (after the initial discovery needed for bootstrapping)?
This could be a complementary mechanism for multicast based
discovery, especially for a very large autonomic network.
Centralized registration could be automatically deployed
incrementally. At the very first stage, the repository could be
empty; then it could be filled in by the objectives discovered by
different devices (for example using Dynamic DNS Update). The
more records are stored in the repository, the less the multicast-
based discovery is needed. However, if we adopt such a mechanism,
there would be challenges: stateful solution, and security.
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RESOLVED for now by adding optional use of DNS-SD by ASAs.
o 5. Need to expand description of the minimum requirements for the
specification of an individual discovery, synchronization or
negotiation objective.
o 6. Use case and protocol walkthrough. A description of how a
node starts up, performs discovery, and conducts negotiation and
synchronisation for a sample use case would help readers to
understand the applicability of this specification. Maybe it
should be an artificial use case or maybe a simple real one, based
on a conceptual API. However, the authors have not yet decided
whether to have a separate document or have it in the protocol
document.
o 7. Cross-check against other ANIMA WG documents for consistency
and gaps.
o 8. Consideration of ADNCP proposal.
RESOLVED by adding optional use of ADNCP for flooding-type
synchronization.
o 9. Clarify how a GDNP instance knows whether it is running inside
the ACP. (Sheng)
RESOLVED by improved text.
o 10. Clarify how a non-ACP GDNP instance initiates (D)TLS.
(Sheng)
RESOLVED by improved text and declaring DTLS out of scope for this
draft.
o 11. Clarify how UDP/TCP choice is made. (Sheng) [Like DNS? -
Brian]
RESOLVED by improved text.
o 12. Justify that IP address within ACP or (D)TLS environment is
sufficient to prove AN identity; or explain how Device Identity
Option is used. (Sheng)
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RESOLVED for now: we assume that all ASAs in a device are trusted
as soon as the device is trusted, so they share credentials. In
that case the Device Identity Option is useless. This needs to be
reviewed later.
o 13. Emphasise that negotiation/synchronization are independent
from discovery, although the rapid discovery mode includes the
first step of a negotiation/synchronization. (Sheng)
RESOLVED by improved text.
o 14. Do we need an unsolicited flooding mechanism for discovery
(for discovery results that everyone needs), to reduce scaling
impact of flooding discovery messages? (Toerless)
RESOLVED: Yes, added to requirements and solution.
o 15. Do we need flag bits in Objective Options to distinguish
distinguish Synchronization and Negotiation "Request" or rapid
mode "Discovery" messages? (Bing)
RESOLVED: yes, work on the API showed that these flags are
essential.
o 16. (Related to issue 14). Should we revive the "unsolicited
Response" for flooding synchronisation data? This has to be done
carefully due to the well-known issues with flooding, but it could
be useful, e.g. for Intent distribution, where DNCP doesn't seem
applicable.
o 17. Ensure that the discovery mechanism is completely proof
against loops and protected against duplicate responses.
o 18. Discuss the handling of multiple valid discovery responses.
o 19. Should we use a text-oriented format such as JSON/CBOR
instead of native binary TLV format?
o 20. Is the Divert option needed? If a discovery response
provides a valid IP address or FQDN, the recipient doesn't gain
any extra knowledge from the Divert.
o 21. Rename the protocol as GRASP (GeneRic Autonomic Signaling
Protocol)?
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5. Security Considerations
It is obvious that a successful attack on negotiation-enabled nodes
would be extremely harmful, as such nodes might end up with a
completely undesirable configuration that would also adversely affect
their peers. GDNP nodes and messages therefore require full
protection.
- Authentication
A cryptographically authenticated identity for each device is
needed in an autonomic network. It is not safe to assume that a
large network is physically secured against interference or that
all personnel are trustworthy. Each autonomic device MUST be
capable of proving its identity and authenticating its messages.
GDNP relies on a separate certificate-based security mechanism to
support authentication, data integrity protection, and anti-replay
protection.
Since GDNP is intended to be deployed in a single administrative
domain operating its own trust anchor and CA, there is no need for
a trusted public third party. In a network requiring "air gap"
security, such a dependency would be unacceptable.
- Privacy and confidentiality
Generally speaking, no personal information is expected to be
involved in the signaling protocol, so there should be no direct
impact on personal privacy. Nevertheless, traffic flow paths,
VPNs, etc. could be negotiated, which could be of interest for
traffic analysis. Also, operators generally want to conceal
details of their network topology and traffic density from
outsiders. Therefore, since insider attacks cannot be excluded in
a large network, the security mechanism for the protocol MUST
provide message confidentiality.
- DoS Attack Protection
GDNP discovery partly relies on insecure link-local multicast.
Since routers participating in GDNP sometimes relay discovery
messages from one link to another, this could be a vector for
denial of service attacks. Relevant mitigations are specified in
Section 3.3.3. Additionally, it is of great importance that
firewalls prevent any GDNP messages from entering the domain from
an untrusted source.
- Security during bootstrap and discovery
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A node cannot authenticate GDNP traffic from other nodes until it
has identified the trust anchor and can validate certificates for
other nodes. Also, until it has succesfully enrolled
[I-D.pritikin-anima-bootstrapping-keyinfra] it cannot assume that
other nodes are able to authenticate its own traffic. Therefore,
GDNP discovery during the bootstrap phase for a new device will
inevitably be insecure and GDNP synchronization and negotiation
will be impossible until enrollment is complete.
6. IANA Considerations
Section 3.4 defines the following link-local multicast addresses,
which have been assigned by IANA for use by GDNP:
ALL_GDNP_NEIGHBOR multicast address (IPv6): (TBD1). Assigned in the
IPv6 Link-Local Scope Multicast Addresses registry.
ALL_GDNP_NEIGHBOR multicast address (IPv4): (TBD2). Assigned in the
IPv4 Multicast Local Network Control Block.
(Note in draft: alternatively, we could use 224.0.0.1, currently
defined as All Systems on this Subnet.)
Section 3.4 defines the following UDP and TCP port, which has been
assigned by IANA for use by GDNP:
GDNP Listen Port: (TBD3)
This document defines the General Discovery and Negotiation Protocol
(GDNP). The IANA is requested to create a GDNP registry within the
unused portion of the DNCP registry [I-D.ietf-homenet-dncp]. The
IANA is also requested to add two new registry tables to the newly-
created GDNP registry. The two tables are the GDNP Messages table
and GDNP Options table.
Initial values for these registries are given below. Future
assignments are to be made through Standards Action or Specification
Required [RFC5226]. Assignments for each registry consist of a type
code value, a name and a document where the usage is defined.
Note to the RFC Editor: In the following tables and in the body of
this document, the values G0, G1, etc., should be replaced by the
assigned values.
GDNP Messages table. The values in this table are 16-bit unsigned
integers. The following initial values are assigned in Section 3.6
in this document:
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Type | Name | RFCs
---------+-----------------------------+------------
G0 |Reserved | this document
G1 |Discovery Message | this document
G2 |Response Message | this document
G3 |Request Message | this document
G4 |Negotiation Message | this document
G5 |Negotiation-ending Message | this document
G6 |Confirm-waiting Message | this document
G7~31 |reserved for future messages |
GDNP Options table. The values in this table are 16-bit unsigned
integers. The following initial values are assigned in Section 3.7
and Section 3.8.1 in this document:
Type | Name | RFCs
---------+-----------------------------+------------
G32 |Divert Option | this document
G33 |Accept Option | this document
G34 |Decline Option | this document
G35 |Waiting Time Option | this document
G36 |Device Identity Option | this document
G37 |Locator IPv4 Address Option | this document
G38 |Locator IPv6 Address Option | this document
G39 |Locator FQDN Option | this document
G40~63 |Reserved for future GDNP |
|General Options |
G64~127 |Reserved for future GDNP |
|Objective Options |
G128~159|Vendor Specific Options | this document
G160~175|Reserved for future use |
G176~191|Experimental Options | this document
G192~???|Reserved for future use |
7. Acknowledgements
A major contribution to the original version of this document was
made by Sheng Jiang.
Valuable comments were received from Michael Behringer, Jeferson
Campos Nobre, Laurent Ciavaglia, Zongpeng Du, Yu Fu, Zhenbin Li,
Dimitri Papadimitriou, Michael Richardson, Markus Stenberg, Rene
Struik, Dacheng Zhang, and other participants in the NMRG research
group and the ANIMA working group.
This document was produced using the xml2rfc tool [RFC2629].
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8. Change log [RFC Editor: Please remove]
draft-carpenter-anima-discovery-negotiation-protocol-04, 2015-06-21:
Tuned wording around hierarchical structure.
Changed "device" to "ASA" in many places.
Reformulated requirements to be clear that the ASA is the main
customer for signaling.
Added requirement for flooding unsolicited synch, and added it to
protocol spec. Recognized DNCP as alternative for flooding synch
data.
Requirements clarified, expanded and rearranged following design team
discussion.
Clarified that GDNP discovery must not be a prerequisite for GDNP
negotiation or synchronization (resolved issue 13).
Specified flag bits for objective options (resolved issue 15).
Clarified usage of ACP vs TLS/DTLS and TCP vs UDP (resolved issues
9,10,11).
Updated DNCP description from latest DNCP draft.
Editorial improvements.
draft-carpenter-anima-discovery-negotiation-protocol-03, 2015-04-20:
Removed intrinsic security, required external security
Format changes to allow ADNCP co-existence
Recognized DNS-SD as alternative discovery method.
Editorial improvements
draft-carpenter-anima-discovery-negotiation-protocol-02, 2015-02-19:
Tuned requirements to clarify scope,
Clarified relationship between types of objective,
Clarified that objectives may be simple values or complex data
structures,
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Improved description of objective options,
Added loop-avoidance mechanisms (loop count and default timeout,
limitations on discovery relaying and on unsolicited responses),
Allow multiple discovery objectives in one response,
Provided for missing or multiple discovery responses,
Indicated how modes such as "dry run" should be supported,
Minor editorial and technical corrections and clarifications,
Reorganized future work list.
draft-carpenter-anima-discovery-negotiation-protocol-01, restructured
the logical flow of the document, updated to describe synchronization
completely, add unsolicited responses, numerous corrections and
clarifications, expanded future work list, 2015-01-06.
draft-carpenter-anima-discovery-negotiation-protocol-00, combination
of draft-jiang-config-negotiation-ps-03 and draft-jiang-config-
negotiation-protocol-02, 2014-10-08.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
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9.2. Informative References
[I-D.behringer-anima-autonomic-control-plane]
Behringer, M., Bjarnason, S., BL, B., and T. Eckert, "An
Autonomic Control Plane", draft-behringer-anima-autonomic-
control-plane-02 (work in progress), March 2015.
[I-D.behringer-anima-reference-model]
Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
and B. Liu, "A Reference Model for Autonomic Networking",
draft-behringer-anima-reference-model-02 (work in
progress), June 2015.
[I-D.chaparadza-intarea-igcp]
Behringer, M., Chaparadza, R., Petre, R., Li, X., and H.
Mahkonen, "IP based Generic Control Protocol (IGCP)",
draft-chaparadza-intarea-igcp-00 (work in progress), July
2011.
[I-D.eckert-anima-stable-connectivity]
Eckert, T. and M. Behringer, "Using Autonomic Control
Plane for Stable Connectivity of Network OAM", draft-
eckert-anima-stable-connectivity-01 (work in progress),
March 2015.
[I-D.ietf-dnssd-requirements]
Lynn, K., Cheshire, S., Blanchet, M., and D. Migault,
"Requirements for Scalable DNS-SD/mDNS Extensions", draft-
ietf-dnssd-requirements-06 (work in progress), March 2015.
[I-D.ietf-homenet-dncp]
Stenberg, M. and S. Barth, "Distributed Node Consensus
Protocol", draft-ietf-homenet-dncp-05 (work in progress),
June 2015.
[I-D.ietf-homenet-hncp]
Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", draft-ietf-homenet-hncp-06 (work in
progress), June 2015.
[I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-05 (work in
progress), June 2015.
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[I-D.liang-iana-pen]
Liang, P., Melnikov, A., and D. Conrad, "Private
Enterprise Number (PEN) practices and Internet Assigned
Numbers Authority (IANA) registration considerations",
draft-liang-iana-pen-05 (work in progress), March 2015.
[I-D.pritikin-anima-bootstrapping-keyinfra]
Pritikin, M., Behringer, M., and S. Bjarnason,
"Bootstrapping Key Infrastructures", draft-pritikin-anima-
bootstrapping-keyinfra-01 (work in progress), February
2015.
[I-D.stenberg-anima-adncp]
Stenberg, M., "Autonomic Distributed Node Consensus
Protocol", draft-stenberg-anima-adncp-00 (work in
progress), March 2015.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day,
"Service Location Protocol, Version 2", RFC 2608, June
1999.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)", RFC
2865, June 2000.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3416] Presuhn, R., "Version 2 of the Protocol Operations for the
Simple Network Management Protocol (SNMP)", STD 62, RFC
3416, December 2002.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
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[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet
Signalling Transport", RFC 5971, October 2010.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, March 2011.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
Bierman, "Network Configuration Protocol (NETCONF)", RFC
6241, June 2011.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
February 2013.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, February 2013.
[RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
2013.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, May 2014.
[RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking: Definitions and Design Goals", RFC 7575, June
2015.
[RFC7576] Jiang, S., Carpenter, B., and M. Behringer, "General Gap
Analysis for Autonomic Networking", RFC 7576, June 2015.
Appendix A. Capability Analysis of Current Protocols
This appendix discusses various existing protocols with properties
related to the above negotiation and synchronisation requirements.
The purpose is to evaluate whether any existing protocol, or a simple
combination of existing protocols, can meet those requirements.
Numerous protocols include some form of discovery, but these all
appear to be very specific in their applicability. Service Location
Protocol (SLP) [RFC2608] provides service discovery for managed
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networks, but requires configuration of its own servers. DNS-SD
[RFC6763] combined with mDNS [RFC6762] provides service discovery for
small networks with a single link layer.
[I-D.ietf-dnssd-requirements] aims to extend this to larger
autonomous networks. However, both SLP and DNS-SD appear to target
primarily application layer services, not the layer 2 and 3
objectives relevant to basic network configuration. Both SLP and
DNS-SD are text-based protocols.
Routing protocols are mainly one-way information announcements. The
receiver makes independent decisions based on the received
information and there is no direct feedback information to the
announcing peer. This remains true even though the protocol is used
in both directions between peer routers; there is state
synchronization, but no negotiation, and each peer runs its route
calculations independently.
Simple Network Management Protocol (SNMP) [RFC3416] uses a command/
response model not well suited for peer negotiation. Network
Configuration Protocol (NETCONF) [RFC6241] uses an RPC model that
does allow positive or negative responses from the target system, but
this is still not adequate for negotiation.
There are various existing protocols that have elementary negotiation
abilities, such as Dynamic Host Configuration Protocol for IPv6
(DHCPv6) [RFC3315], Neighbor Discovery (ND) [RFC4861], Port Control
Protocol (PCP) [RFC6887], Remote Authentication Dial In User Service
(RADIUS) [RFC2865], Diameter [RFC6733], etc. Most of them are
configuration or management protocols. However, they either provide
only a simple request/response model in a master/slave context or
very limited negotiation abilities.
There are some signaling protocols with an element of negotiation.
For example Resource ReSerVation Protocol (RSVP) [RFC2205] was
designed for negotiating quality of service parameters along the path
of a unicast or multicast flow. RSVP is a very specialised protocol
aimed at end-to-end flows. However, it has some flexibility, having
been extended for MPLS label distribution [RFC3209]. A more generic
design is General Internet Signalling Transport (GIST) [RFC5971], but
it is complex, tries to solve many problems, and is also aimed at
per-flow signaling across many hops rather than at device-to-device
signaling. However, we cannot completely exclude extended RSVP or
GIST as a synchronization and negotiation protocol. They do not
appear to be directly useable for peer discovery.
We now consider two protocols that are works in progress at the time
of this writing. Firstly, RESTCONF [I-D.ietf-netconf-restconf] is a
protocol intended to convey NETCONF information expressed in the YANG
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language via HTTP, including the ability to transit HTML
intermediaries. While this is a powerful approach in the context of
centralised configuration of a complex network, it is not well
adapted to efficient interactive negotiation between peer devices,
especially simple ones that are unlikely to include YANG processing
already.
Secondly, we consider Distributed Node Consensus Protocol (DNCP)
[I-D.ietf-homenet-dncp]. This is defined as a generic form of state
synchronization protocol, with a proposed usage profile being the
Home Networking Control Protocol (HNCP) [I-D.ietf-homenet-hncp] for
configuring Homenet routers. A specific application of DNCP for
autonomic networking was proposed in [I-D.stenberg-anima-adncp].
DNCP "is designed to provide a way for each participating node to
publish a set of TLV (Type-Length-Value) tuples, and to provide a
shared and common view about the data published... DNCP is most
suitable for data that changes only infrequently... If constant rapid
state changes are needed, the preferable choice is to use an
additional point-to-point channel..."
Specific features of DNCP include:
o Every participating node has a unique node identifier.
o DNCP messages are encoded as a sequence of TLV objects, sent over
unicast UDP or TCP, with or without (D)TLS security.
o Multicast is used only for discovery of DNCP neighbors when lower
security is acceptable.
o Synchronization of state is maintained by a flooding process using
the Trickle algorithm. There is no bilateral synchronization or
negotiation capability.
o The HNCP profile of DNCP is designed to operate between directly
connected neighbors on a shared link using UDP and link-local IPv6
addresses.
DNCP does not meet the needs of a general negotiation protocol,
because it is designed specifically for flooding synchronization.
Also, in its HNCP profile it is limited to link-local messages and to
IPv6. However, at the minimum it is a very interesting test case for
this style of interaction between devices without needing a central
authority, and it is a proven method of network-wide state
synchronization by flooding.
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A proposal was made some years ago for an IP based Generic Control
Protocol (IGCP) [I-D.chaparadza-intarea-igcp]. This was aimed at
information exchange and negotiation but not directly at peer
discovery. However, it has many points in common with the present
work.
None of the above solutions appears to completely meet the needs of
generic discovery, state synchronization and negotiation in a single
solution. Neither is there an obvious combination of protocols that
does so. Therefore, this document proposes the design of a protocol
that does meet those needs. However, this proposal needs to be
compared with alternatives such as extension and adaptation of GIST
or DNCP, or combination with IGCP.
Authors' Addresses
Brian Carpenter
Department of Computer Science
University of Auckland
PB 92019
Auckland 1142
New Zealand
Email: brian.e.carpenter@gmail.com
Bing Liu
Huawei Technologies Co., Ltd
Q14, Huawei Campus
No.156 Beiqing Road
Hai-Dian District, Beijing 100095
P.R. China
Email: leo.liubing@huawei.com
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